The present invention relates to an Sb—Te alloy sintered compact sputtering target capable of effectively inhibiting the generation of particles.
In recent years, a thin film formed from an Sb—Te material as the phase-change recording material is being used as a medium for recording information using so-called phase transformation. As a method of forming a thin film formed from an Sb—Te alloy material, a generally employed means known as a physical deposition method such as a vacuum deposition method or a sputtering method is used. In particular, a magnetron sputtering method is often used for forming such a thin film from the perspective of operability and coating stability.
Formation of a film according to the sputtering method is conducted by physically colliding positive ions such as Ar ions to a target disposed on a negative electrode, discharging the material configuring the target with such collision energy, and laminating a film having approximately the same composition as the target material on a substrate on the opposite positive electrode side.
Coating according to the sputtering method is characterized in that it is able to form thin films of angstrom units and thick films of several ten μm with a stable deposition speed by adjusting the treating time and power supply.
A particular problem when forming a film formed with an Sb—Te alloy material for a phase-change recording film is the generation of particles during sputtering, generation of nodules (protrusions) that causes abnormal electrical discharge (micro arcing) or cluster-shaped thin films (films that get adhered as a cluster), generation of cracks or fractures of targets during sputtering, and absorption of large quantities of oxygen during the manufacturing process of sintering powder for targets. One reason for this is in the absorption of gas components such as large quantities of oxygen during the manufacture process of the target sintering powder.
The foregoing problems concerning the target or sputtering process are significant cause in deteriorating the quality of the thin film as the recording medium.
It is known that the foregoing problems are significantly influenced by the grain size of the sintering powder or the structure and quality of the target. Nevertheless, conventionally, since it was not possible to manufacture an appropriate amount of powder upon manufacturing an Sb—Te alloy sputtering target for forming a phase-change recording layer, and because there was no available manufacturing method capable of inhibiting these influences, it was not possible to avoid the generation of particles, abnormal electrical discharge, generation of nodules, and generation of cracks or fractures of the target during sputtering, or the inclusion of a large quantity of oxygen in the target.
As a conventional manufacturing method of a Ge—Sb—Te sputtering target, disclosed is a manufacturing method of a Ge—Sb—Te sputtering target including the steps of preparing powder by performing inert gas atomization to a Ge—Te alloy and an Sb—Te alloy, uniformly mixing the alloys having a ratio of Ge/Te=1/1 and Sb/Te=0.5 to 2.0 , and thereafter performing pressure sintering thereto (for instance, refer to Patent Document 1).
Further, disclosed is a manufacturing method of a Ge—Sb—Te sputtering target and technology for manufacturing powder to be used therein employing the atomization method, including the steps of casting powder among the alloy powder containing Ge, Sb, Te in which the tap density (relative density) is 50% or greater into a mold, performing cold or hot pressurization thereto, and sintering the molding material in which the density after cold pressurization is 95% or greater through heat treatment in an Ar or vacuum atmosphere so as to make the oxygen content in the sintered compact 700 ppm or less (for instance, refer to Patent Document 2).
Further, disclosed is a manufacturing method of a Ge—Sb—Te sputtering target material including the steps of preparing rapidly-cooled powder by the inert gas atomization method from a raw material containing Ge, Sb, Te, and sintering a compact subject to cold or hot pressure forming using powder among said powder that is 20 μm or greater and having a particle size distribution where the specific surface area per unit weight is 300 mm2/g or less (for instance, refer to Patent Document 3).
Other technologies for manufacturing targets using atomized powder are described in Patent Documents 4, 5, 6 indicated below.
Nevertheless, since the foregoing Patent Documents use the atomized powder as is, they are not able to obtain sufficient target strength, and it can hardly be said that they have achieved the refinement and homogenization of the target structure. Further, the tolerated oxygen content is high, and there is a problem in that the foregoing technologies are insufficient as an Sb—Te sputtering target for forming a phase-change recording layer.
Further, also known is a sputtering target for forming an optical disk recording layer in which the surface-oxidized layer and processing layer are removed, and having a surface roughness (center line average roughness) Ra≦1.0 μm (refer to Patent Document 7). The object of this target is to shorten the pre-sputter time and to eliminate pre-sputtering all together, and is extremely effect in achieving these objects.
Nevertheless, recent DVDs and BDs (Blu-Ray Discs) demand even high density, and the reduction of particles generated in the targets is extremely important in order to improve the production yield.
Thus, in addition to shortening the pre-sputter time as described above, it is necessary to improve the overall quality of the target, and not only the target surface, in order to effectively inhibit the generation of particles, abnormal discharge, generation of nodules, generation of cracks or fractures in the target and so on.
[Patent Document 1]
    Japanese Patent Laid-Open Publication No. 2000-265262[Patent Document 2]    Japanese Patent Laid-Open Publication No. 2001-98366[Patent Document 3]    Japanese Patent Laid-Open Publication No. 2001-123266[Patent Document 4]    Japanese Patent Laid-Open Publication No. S10-81962[Patent Document 5]    Japanese Patent Laid-Open Publication No. 2001-123267[Patent Document 6]    Japanese Patent Laid-Open Publication No. 2000-129316[Patent Document 7]    Japanese Patent Laid-Open Publication No. 2000-169960